<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>盒子模型</title>
    <style>
        .wai{

        }
        .nei {


        }
    </style>
</head>
<body>
<div class="wai">
    <div class="nei">

    </div>
</div>
</body>
</html>